1. Field of the Invention
The present invention relates generally to apparatus for monitoring a data bus. In particular, the present invention relates to an apparatus which allows a notebook computer or the like to monitor data transmission via an RS-232 bus.
2. Description of the Prior Art
There is currently a need to monitor communications or data transmission between data terminal equipment and data set equipment which takes place over an RS-232 bus. While it is relatively simple to monitor transmit or receive data independently, it is very difficult to monitor both transmit and receive communications simultaneously.
Commercially available monitoring systems generally monitor communications via the RS-232 bus in only one direction, either transmit data or receive data is monitored, but not data transmission in both directions. Generally, RS-232 bus monitoring devices are relatively simple wire taps or tees.
There is, however, a need for a monitoring apparatus which allows the user to simultaneously monitor transmit and receive data of half duplex communications taking place over a full duplex RS-232 bus with a single port RS-232 connection to a personal computer.
The present invention overcomes some of the difficulties of the past including those mentioned above in that it comprises a relatively simple in design yet highly effective and efficient monitoring apparatus for use in monitoring data communications via the RS-232 bus between data terminal equipment and data set equipment.
The monitoring apparatus of the present invention allows the user to monitor transmit and receive data of half duplex communications taking place over a full duplex RS-232 bus and also monitor full duplex communications on the RS-232 bus. The monitoring apparatus includes six switching transistors which are turned on and off depending on input voltage levels appearing at the transmit and receive lines input to the monitoring apparatus from the RS-232 bus. Turning on and off the switching transistors enables a computer, lap top or other device connected to the monitoring apparatus to receive and process data communications on the RS-232 bus.